The role of the Histology Laboratory Core is to coordinate and provide professional and technical services for proper handling and processing of histopathologic materials. Specific aims are: 1) to prepare routine hematoxylin and eosin (H&E)-stained pathology slides and provide histopathologic characteristics of biopsy materials; 2) to perform and core Ki-67 immunohistochemical staining on bronchial biopsy samples for Project 1; 3) to prepare and distribute unstained tissue sections required for special histopathologic examinations and in situ hybridization studies; 4) to assist in the interpretation and evaluation of biomarker analysis. The main purpose of this project is to develop effective chemopreventive approaches in current and former smokers and to identify potentially useful biomarkers of intermediate endpoints. We expect to deal with a large bulk of histopathologic materials in this project. In addition, some studies require special care in preparing the tissue sections. For example, for the in situ mRNA hybridization studies, the slide should be prepared using specially treated water to avoid RNA degradation, which cannot be accommodated by the regular pathology department personnel. Therefore, it is essential to establish a separate core facility for successful control of this project. As the clinical trial progresses to attain the targeted sample size, more core effort will be required in the preparation and distribution of tissue sections for the translational research projects. The role of this core will become increasingly important because proposed studies and further progress in the field of carcinogenesis research may identify new cellular, biochemical, or molecular genetic markers of interest. These will need to be tested and expanded using the tissue samples obtained through this project.